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| 1.
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Nakano, Tomoyuki ; Tanaka, Yasunori ; Murai, Kosuke ; Uesugi, Yoshihiko ; Ishijima, Tatsuo ; Tomita, Kensuke ; Suzuki, Katsumi ; Shinkai, Takeshi ; 田中, 康規 ; 上杉, 喜彦 ; 石島, 達夫
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金沢大学理工研究域電子情報学系<br />This paper presents the arc quenching abilities of various gases studied using a power semiconducto
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r switching technique. The technique uses an insulated gate bi-polar transistor (IGBT) to inject current and apply voltage to the plasma arc. Using this technique, arcs in free recovery condition after a 50 A steady state condition were investigated in SF6, CO2, O2, N2, air and Ar gas flows. Furthermore, at a specific time high voltages of about 1.1 kV and 1.7 kV μ were applied to the residual decaying arcs by the IGBT to elucidate the arc re-ignition process and recovery properties. These systematic experiments further enabled us to estimate the interruption probability versus the voltage application time. From these results, the voltage application time for 50% successful interruption was estimated for various gases, with the results showing a direct relation to the interruption capabilities of the respective gases. These results were then compared to the electron density measurement results and numerical simulation results to confirm their validity. All data obtained from the experiments and simulation is expected to be useful for elucidating the arc quenching physics and also for the practical application of arc quenching phenomena. © 2017 IOP Publishing Ltd.<br />Embargo Period 12 months
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| 2.
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Tanaka, Yasunori ; Sakai, H. ; Tsuke, T. ; Uesugi, Yoshihiko ; Sakai, Y. ; Nakamura, K.
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金沢大学理工研究域<br />This paper describes the relation between the size of synthesized nanoparticles and the temperature varia
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tion of the surrounding plasma in TiO2 nanoparticle synthesis using pulse-modulated induction thermal plasmas (PMITP). The Ar-O2 PMITP at 20 kW was used to obtain repetitional temperature fields at pressure of 200 Torr. The TiO2 nanoparticles were synthesized by direct injection of Ti powder with mean diameter of 45 μm. Dependence of the nanoparticle size on modulation parameters such as the duty factor and the shimmer current level of the PMITP were investigated experimentally. Instantaneous temperature evolution was evaluated through spectroscopic observation. Experimental results show that the temperature decay rate in the PMITP reached 105106 K/s, and that the mean diameter of synthesized particles decreased with the temperature decay rate. © 2010 Elsevier B.V. All rights reserved.
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| 3.
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Tanaka, Yasunori ; Sakai, H. ; Tsuke, T. ; Uesugi, Yoshihiko ; Sakai, Y. ; Nakamura K.
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This paper describes the relation between the size of synthesized nanoparticles and the temperature variation of the sur
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rounding plasma in TiO2 nanoparticle synthesis using pulse-modulated induction thermal plasmas (PMITP). The Ar-O2 PMITP at 20 kW was used to obtain repetitional temperature fields at pressure of 200 Torr. The TiO2 nanoparticles were synthesized by direct injection of Ti powder with mean diameter of 45 μm. Dependence of the nanoparticle size on modulation parameters such as the duty factor and the shimmer current level of the PMITP were investigated experimentally. Instantaneous temperature evolution was evaluated through spectroscopic observation. Experimental results show that the temperature decay rate in the PMITP reached 105106 K/s, and that the mean diameter of synthesized particles decreased with the temperature decay rate. © 2010 Elsevier B.V.
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| 4.
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Sasaki, Aya ; Takai, Yuichiro ; Uesugi, Yoshihiko ; Tanaka, Yasunori ; Ishijima, T. ; Masuzaki, Suguru
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Control of tritium retention and its removal from the first wall of future fusion devices are the most crucial issues fo
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r safety and effective use of the fuel. Nitrogen injection into edge plasmas has been considered and tested as an effective method for suppression of carbon dust growth and reduction of hydrogen isotope inventory. In this paper we have investigated scavenger effects of nitrogen injected into H2/CH4 plasmas using a small helical device where low density (ne ∼ 1016 m-3) and low temperature (Te = 5-10 eV) hydrogen plasmas are generated in steady state condition like remote plasmas in fusion devices. It is shown from the comparison of the carbon film deposition and particle growth between those with and without N2 injection that the chemical erosion effects of nitrogen gas on the carbon film and particle growth strongly depends on the surface temperature. With increasing the surface temperature higher than ∼400 K, the nitrogen chemical erosion significantly works to reduce the hydrocarbon deposition. © 2013 Elsevier B.V. All rights reserved.
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Tanaka, Yasunori ; Tsuke, Tatsuya ; Guo, Weixuan ; Uesugi, Yoshihiko ; Ishijima, Tatsuo ; Watanabe, Shu ; Nakamura, Keitaro
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A large amount synthesis method for titanium dioxide (TiO2) nanopowder is proposed by direct evaporation of titanium powders using Ar-O 2 pulse-modulated induction thermal plasma (PMITP). To realize a large amount synthesis of
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nanopowder, the PMITP method was combined with the intermittent and heavy load feeding of raw material powder, as well as the quenching gas injection. The intermittent powder feeding was synchronized with the modulation of the coil current sustaining the PMITP for complete evaporation of the injected powder. Synthesized particles by the developed method were analyzed by FE-SEM and XRD. Results indicated that the synthesized particles by the 20-kW PMITP with a heavy loading rate of 12.3 g min-1 had a similar particle size distribution with the mean diameter about 40 nm to those with light loading of 4.2 g min-1.
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6. Spallation occurrence from polyamide materials irradiated by thermal plasma with water absorption
Nakano, Tomoyuki ; Tanaka, Yasunori ; Nakagawa, Takuya ; Shinsei, Naoki . ; Uesugi, Yoshihiko ; Ishijima, Tatsuo
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This paper first describes the effect of water absorption in polyamide material irradiated by thermal plasmas on the occ
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urrence of spallation phenomena. The interaction between polyamide materials and arc plasmas occurs particularly in the low voltage circuit breaker and aerospace fields. Spallation phenomena are those in which polymer particles are ejected from polymer bulk materials irradiated by high heat flux. To confirm the effect of water absorption into the polyamide material on spallation phenomena, polyamide specimens with and without water absorption were irradiated by Ar inductively coupled thermal plasma. The results show that the polyamide specimen with water absorption ejected spallation particles, whereas the polyamide specimen without water absorption were only slightly ejected, indicating that water absorption promotes the occurrence of spallation. The cooling effects of the spallation polyamide 66 (PA66) particles ablation were also estimated in hot air to assess the arc quenching ability from the spallation particle inclusion. This estimation showed that 10 and more PA66 particles inclusion might decrease the air temperature by 3000 K effectively, which can be useful to enhance arc quenching in circuit breakers working in air. © 2016 IOP Publishing Ltd.<br />Embargo Period 12 months
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| 7.
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Tanaka, Yasunori ; Suzuki, Katsumi ; Iijima, Takanori ; Shinkai, Takeshi
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This paper describes the development of a model with both chemically and thermally non-equilibrium effects in an SF6 arc
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plasma during decaying phase with transient recovery voltage (TRV) application. The SF 6 arc plasma in decaying phase can be seen in a high voltage SF 6 gas circuit breaker during a large current interruption process. The TRV is often applied to the arc plasma, which may elevate the electron temperature Te than heavy particle temperature Th. This developed model solves energy equations for electrons and heavy particles, accounting for totally 122 reactions due to 19 species in SF6 arc plasmas. As a result, transient distributions of Te and Th were calculated for SF6 arc plasma in a TRV application condition for a fundamental study. © 2013 IEEE.
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| 8.
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Nakano, Tomoyuki ; Shinsei, Naoki ; Ishida, Masahiro ; Tanaka, Yasunori ; Uesugi, Yoshihiko ; Ishijima, Tatsuo
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This paper reports enhancement effect of N2/O2 gas addition in thermal plasma irradiation on the spallation phenomena fr
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om polyamide-66 (PA66) specimens with water absorption. The polyamide materials are widely used, for example, in low-voltage circuit breakers and arcing horns as ablation material. In such devices, the polymer is often contacted with arc discharges to be ablated, which increases the arc current interruption ability of the circuit breakers. In our previous experiments, not only ablation but also spallation phenomena had been found to occur from PA66 specimens with water absorption by Ar thermal plasma irradiation. The present work was conducted to investigate effect of N2/O2 inclusion in the irradiating thermal plasma on the occurrence of spallation phenomena because the air circuit breaker was used in air. Relative oxygen admixture ratio to N2 was changed from 0% to 100% with a fixed heat flux irradiated to PA66 specimens. Results indicated that O2 inclusion effectively promotes the frequency of spallation particle ejection from PA66 specimen with 3 wt% water absorption. © 2013 IEEE.
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| 9.
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Kodama, Naoto ; Tanaka, Yasunori ; Kita, K. ; Uesugi, Yoshihiko ; Ishijima, T. ; Watanabe, S. ; Nakamura, K.
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A unique method of large-scale synthesis of Al-doped TiO2 nanopowder was developed, using 20kW Ar-O2 pulse-modulated ind
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uction thermal plasmas (PMITP) with time-controlled feedstock feeding (TCFF). This PMITP-TCFF method is characterized by intermittent feedstock powder feeding synchronized with modulation of the power of the PMITP. The method enables heavy-load feeding of raw material powder to the thermal plasmas for complete evaporation. The nanopowder synthesized was analysed using different methods including field emission scanning electron microscopy, x-ray diffraction (XRD) spectroscopy, bright-field transmission electron microscopy (TEM), TEM/energy dispersive x-ray (EDX) mapping, x-ray photoelectron spectroscopy, and spectrophotometry. The results showed that Al-doped TiO2 nanopowder can be synthesized with mean diameters of 50-60nm. The Al doping in TiO 2 was confirmed from the constituent structure in the XRD spectra, the uniform presence of Al in the nanopowder in the TEM/EDX mapping, the chemical shift in the x-ray photoelectron spectra, and the absorption edge shift in the optical properties. The rate of production of the Al-doped TiO 2 nanopowder was estimated as 400gh-1. © 2014 IOP Publishing Ltd.
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| 10.
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Long, Nguyen Phi ; Tanaka, Yasunori ; Uesugi, Yoshihiko
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Evaporation of hafnium cathode in a plasma cutting arc torch was investigated numerically and experimentally to assess t
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he effects of cathode diameter and operating parameters such as gas pressure, gas flow rate and arc current. A numerical model was developed for arc plasma with consideration of hafnium cathode evaporation. Using this model, the surface cathode temperature and the amount of cathode mass loss caused by evaporation were predicted for different operating parameters. Simulated results show that the cathode surface temperature decreases at the hafnium cathode centre with increasing gas flow rate and cathode diameter. However, an increase in gas pressure elevates the surface cathode temperature in the radial range of 0.35mm. The total amount of mass loss of hafnium cathode evaporation was predicted to be enhanced with increasing gas flow rate, gas pressure and cathode diameter as well. Comparison of the calculated results with experimentally obtained results shows good agreement in terms of the average surface cathode temperature, with variation in gas pressure and cathode diameter. © 2012 IOP Publishing Ltd.
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